ATKeiper writes: Thomas Kuhn's landmark book The Structure of Scientific Revolutions just turned fifty years old. In that book, Kuhn coined the expression 'paradigm shift' to describe revolutionary changes in scientific fields — such as the replacement of the geocentric understanding of the universe with the heliocentric model of the solar system. The book was hotly debated for claiming that different scientific paradigms were 'incommensurable,' which implied (for example) that Newton was no more right about gravity than Aristotle. A new essay in The New Atlantis revisits the controversy and asks whether the fact that Kuhn based his argument almost exclusively on physics means that it does not apply as well to major developments in biology or, for that matter, to the social sciences.